Astronomy: Breaking down stardust forms molecules in space

An alternative explanation for how large carbon-containing molecules might be formed in interstellar space is presented in Nature Communications this week. These molecules, whose formation in space is still a puzzle, are proposed to be formed by breaking up the graphite surface of a stardust particle. This theory is tested by emulating interstellar conditions in an ultrahigh vacuum chamber.

With the help of big radiotelescopes, polycyclic aromatic hydrocarbons - large carbon-containing molecules - could be observed in abundance in interstellar space but why they exist and how they can form in interstellar conditions is still unclear. Many previous formation theories proposed a bottom-up chemical process where small molecules react to form larger molecules. But the bottom-up mechanisms cannot explain the abundance of polycyclic hydrocarbons in space. Pablo Merino, Jose Martin-Gago and colleagues now show that an alternative top-down approach might also play a role in polycyclic hydrocarbon formation in the interstellar medium. Emulating the conditions in space in an ultrahigh vacuum chamber, they show that stardust particles composed of silicon carbide with a graphite surface can be broken down to form polycyclic aromatic hydrocarbons when the dust is exposed to atomic hydrogen. This mechanism could explain the amount of polycyclic hydrocarbons in space.

doi: 10.1038/ncomms4054

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